Avian diseases最新文献

Eastern wild turkeys (Meleagris gallapovo silvestris) in Louisiana have not fully recovered since their decline in the mid-20th century, despite multiple conservation management efforts. Wild turkeys are susceptible to Leucocytozoon infection and also serve as reservoirs of Leucocytozoon parasites. In this study, we tested for Haemosporidian infections (Haemoproteus, Plasmodium, and Leucocytozoon) in 106 different blood samples collected from hunted and live-trapped turkeys in Louisiana using PCR and sequencing of amplicons. Haemoproteus was the most prevalent genus (92%) and had the highest species diversity among the three genera. One-third of our samples were positive for Leucocytozoon infection, significantly less than Haemoproteus but similar to Plasmodium. Male turkeys were more likely to be infected by Leucocytozoon parasites than females. We detected two Leucocytozoon species, Leucocytozoon schoutedeni and Leucocytozoon sabrazesi, the latter possibly being the first detection in North America. There were four times as many turkeys infected with all three genera of Haemosporidia than uninfected turkeys. Last, we present a case study of an emaciated wild turkey in Louisiana; its death was attributed to Leucocytozoon infection. Future research into the pathology of Leucocytozoon infections will clarify whether Leucocytozoon parasites may contribute to population declines in turkeys through mortality or negative reproduction impacts, and whether one sex is more tolerant to Leucocytozoon infection than the other.

Avibacterium paragallinarum is the causative pathogen of infectious coryza. Isolates of A. paragallinarum obtained from China between 2008 and 2022 were characterized using 16S rRNA, HMPt210, multilocus sequence typing, and biochemical tests to assess their genetic and biochemical diversity. All field isolates belonged to the same phylogenetic cluster together based on their 16S rRNA sequences. The similarity of the 16S rRNA sequences between the Chinese field isolates and type strain NCTC11296 was 96.5%-97.0%, and that among the Chinese field isolates was 99.7%-100%. Twenty typeable field isolates were categorized into A-1, B-1, and C-4 clades according to their HMPt210 sequences, but positioned in separate subclades alongside reference strains within each clade. Variable biochemical characteristics were observed between the type strain NCTC11296 and field isolates, with most Chinese field isolates utilizing myo-inositol, L-fucose, arabitol, raffinose, and N-acetyl neuraminic acid, unlike the type strain. The type strain NCTC11296 could produce acid from dextrin and maltose, unlike the 24 Chinese field isolates. Among the 36 isolates tested, one new infB allele and five new sequence types (STs) were identified; the most prevalent ST for Chinese field isolates was ST1 (n = 19; 79.2%). These results suggest that the Chinese field isolates of A. paragallinarum were genetically and biochemically different from the type strain.

This case report details a severe outbreak of acute fowl cholera (FC) in commercial, slow-growing broiler chickens. Three necropsy cases of slow-growing broilers were submitted for postmortem examination at the California Animal Health Food Safety (CAHFS) Laboratory System at three different time points in their production cycle following an acute elevation in mortality on the farm. Broilers were submitted at 5 wk, 11 wk, and 14 wk of age. The birds were submitted from a flock of 25,000 broilers on a 262,500-broiler ranch that experienced 100% mortality by the time of processing at 14 wk of age. Gross findings included petechia, mottled livers and spleens, and congested and edematous lungs. On histology, major findings included hepatic necrosis, splenic necrosis, pulmonary edema, and bacterial colonies proliferation in multiple organs. A definitive diagnosis of FC was made with qPCR detection and aerobic culture and isolation of Pasteurella multocida. The P. multocida isolate was classified as serovar 1, fingerprint profile HhaI 0001 with serotyping and restriction enzyme analysis, respectively. A review of all FC cases detected in avian species submitted to the CAHFS laboratory in the last 11 yr revealed 10 cases of FC in slow-growing broilers and no cases in traditional broilers. This case underscores the need for enhanced biosecurity and potential vaccination strategies in slow-growing poultry systems to mitigate future risks of FC outbreaks.

Avian reovirus (ARV) infections pose a significant economic threat to poultry production despite biocontainment and routine vaccination efforts. Quantifying ARV load is essential for understanding infection dynamics. There is a widespread misperception that ARVs in cultures do not produce countable plaques, leading most in the field to use the less useful 50% tissue culture infectious dose quantifications. Here, we compare the suitability of two well-known avian cell lines, quail myoblast clone 5 (QM5) and leghorn male hepatocellular carcinoma (LMH), for use in plaque assays for the quantification of ARV. LMH cells, which exhibit syncytia formation postinfection, proved unsuitable for plaque assays due to poor substrate adherence, the tendency to form syncytia-like conglomerations of cells even when uninfected, and the tendency for areas of the substrate cleared by viral cytopathic effect (CPE) to quickly fill in with new cell growth. In contrast, QM5 cells demonstrated clear contact inhibition and well-defined CPE, enabling distinct, countable plaques even at high virus titers. Therefore, although LMH cells are advantageous for viral propagation, QM5 cells are better suited for plaque assays to assess ARV infectivity, with QM5 enabling more precise viral growth tracking and quantification.

Major progress has been achieved since the first historical review of infectious bursal disease (H. N. Lasher and V. S. Davis, Avian Diseases, Vol. 41, pp. 11-19; 1997), much of it between 1977 and 2005. Significant findings in the 1980s were the presence of serotype 2 of infectious bursal disease virus (IBDV) and the diversity of antigenic and immunogenic types of IBDV. In the late 1980s, very virulent IBDV strains emerged and became widespread in many countries by the late 1990s. Soon after the discovery of the antigenic variants, specific commercial vaccines were developed and used successfully in the field. The structure of the virus was discovered, which led to the elucidation of virus genes being responsible for some of the virus' biological functions, including immunogenicity. A consequence of these findings was the development of a new class of recombinant vaccines, which were commercially licensed. Reverse genetics became another tool for virus characterization. The development of monoclonal antibodies allowed the identification of immunoglobulin M positive (IgM+) B cells as the major target cells for infection. A role of macrophages and T cells in IBDV pathogenesis and pathology of the bursa of Fabricius was suggested. New tools for serology and virus identification-ELISA and reverse transcriptase (RT) PCR, respectively-provided new insights in the epidemiology. The widespread use of ELISA kits facilitated the use of vaccines in the face of maternally derived antibodies against IBDV, allowing the determination of time of vaccine breakthrough and therefore vaccine administration.

For decades, infectious bronchitis (IB), caused by the infectious bronchitis virus (IBV), has posed a significant threat to poultry health and is mainly controlled by vaccines. However, the currently available commercial vaccines do not provide adequate protection against new IBV strains that emerge due to ongoing evolution. Therefore, new antiviral strategies need to be explored. Cepharanthine (CEP), tetrandrine (TET), and berbamine hydrochloride (BBM) are natural plant-derived bis-benzylisoquinoline alkaloids (BBAs) with proven antiviral activities against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), porcine epidemic diarrhea virus (PEDV), and other viruses. Despite this, their potential antiviral activities against IBV remain unknown. As a proof-of-concept study, we aimed to investigate the inhibitory effects of CEP, TET, and BBM on the laboratory-adapted IBV Beaudette strain in Vero cells and of CEP in chicken embryos. Our research demonstrated that CEP, TET, and BBM effectively suppressed IBV infection in Vero cells, with CEP showing a particularly high selective index of 309.6. These compounds dose-dependently decreased IBV RNA levels and N protein expression and lowered intracellular and extracellular viral titers. Notably, CEP also exhibited antiviral activity against IBV infection in chicken embryos, resulting in reduced mortality and fewer lesions. While these findings highlight the potential of CEP, TET, and BBM as candidates for further development, further studies are required to evaluate their efficacy against field-prevalent IBV strains (e.g., Massachusetts, QX-like) and clarify the specific antiviral mechanisms.

The current case report describes two outbreaks of central nervous system signs associated with Streptococcus gallolyticus subsp. pasteurianus causing encephalitis and meningitis in poults in the U.S. Midwest. Macroscopic lesions observed at necropsy revealed enlarged and pale spleens as well as blood vessel congestion of the meninges. Histopathological examination revealed moderately severe meningoencephalitis with coccoid bacteria detected within the macrophages and mild heterophilic portal hepatitis. Bacterial identification confirmed S. gallolyticus subsp. pasteurianus by matrix-assisted laser desorption time-of-flight mass spectrometry and API 20 STREP strips. Antibiotic sensitivity profiles of the two outbreaks were similar and revealed sensitivity to clindamycin, erythromycin, florfenicol, gentamycin, penicillin, and ceftiofur. Genomic comparisons revealed that the two isolates presented here were identical and encoded for a putative collagen adhesin that could be a potential virulence factor.